The invention relates generally to cutting structures for rotary lawn mowers and so-called weed trimmers and particularly concerns such cutting structures having improved cutting effectiveness and safety characteristics.
While rotary mowing and trimming devices have come into general use both for the consumer and for industry, conventional rigid and semi-rigid cutting blades remain dangerous in use and account for thousands of injuries each year. Even though conventional rigid cutting blades are generally effective for cutting normal vegetation on a lawn, these safety deficiencies have resulted in the development of non-rigid cutting structures which are generally less capable of causing serious injury to a user. However, these non-rigid cutting structures, when sufficiently light in weight to prevent substantial injury, are deficient in their ability to cut normal vegetation encountered even on the typical lawn. All prior cutting structures used primarily for the usual "lawn" mowing are unable to effectively cut heavy vegetation and can not effectively be used unless normal vegetation is relatively dry.
In answer to the deficiencies occasioned by prior art cutting structures, the present invention provides cutting structures useful for mowing vegetation both effectively and safely when compared to prior cutting structures utilized for similar purposes. Further, the present invention provides capabilities to the user of a conventional lawn mower or trimmer which were not previously available. In the context of increased safety, the user of a conventional lawn mower modified according to the present invention allows the clearing and cutting of relatively heavy vegetation in an overgrown field or similar situation without the need for specialized equipment. The same conventional mower modified according to the present invention is also capable of producing a high quality cut on a "normal" lawn. The invention further provides the capability to a user of cutting grass immediately after a rain even though the grass or other vegetation is too wet to be conventionally cut. When adapted to a conventional trimmer, the present invention allows rapid and high quality cutting of vegetation with a degree of efficiency which allows for the first time the cutting of large areas of vegetation with a trimmer and within a reasonably short period of time. The present structures are also capable of bagging mowed vegetation when used with vegetation cutting devices equipped to catch and collect mowed vegetation during the mowing process.
The present structures are particularly useful in that conventional mowing equipment modified according to the invention exhibits increased safety during operation. In particular, in most embodiments of the invention a plate member is employed which effectively shields the cutting surfaces of the structures from other than indirect contact with the hands or feet of a user. Due to the particular structure of the several embodiments of the invention, contact between the cutting surfaces and the user is normally limited to a glancing blow which would not penetrate the skin or cause fracture. The present structures also typically minimize the risk from thrown objects which occur when a conventional lawn mower blade strikes an object such as a rock. Rather than striking such an object a direct blow and causing the object to be thrown with great velocity from the mowing machine, the present structures typically strike the object a glancing blow and "dribbles" the object along the ground from under the mowing machine. The present structures are seen to have inherent safety features which provide substantially reduced risk of injury to a user, these safety features being potentially enhanced by the inclusion of other structure which may be employed on conventional mowing devices for the improvement of safety.
The structures according to the present invention typically comprise a plate member which surmounts a cutting bar which is normally carried by or associated with the plate member. The plate member is typically circular in conformation but can be provided as other geometrical shapes, particularly with rounding off of the corners of such shapes. The cutting bar surmounted by the plate member can also take a variety of forms and can even be integrally formed with the plate member from a material such as metal or plastic. In most embodiments of the invention, the cutter bar is surmounted by the plate member and does not extend beyond the periphery of said plate member. The structures of the present invention are typically mounted to the drive shaft of a conventional mower or trimmer with the cutter bar facing vegetation which is to be cut, the cutter bar typically being shielded from the user by means of the plate member which also acts to deform the vegetation into a favorable position for cutting by the cutter bar.
Accordingly, it is a primary object of the present invention to provide cutting structures useful with mower and trimmer machines, which cutting structures exhibit improved safety capabilities and improved ability to mow and trim vegetation.
Further objects and advantages of the present invention will become more readily apparent in light of the following detailed description of the preferred embodiments.